1. Field of the Invention
The present invention is related to touch operation technique, and more particularly, to an optical sensing system with multi-touch operation functionality.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a conventional optical sensing system 100. The optical sensing system 100 is utilized for detecting a location of a pointing object 102. The optical sensing system 100 includes a sensing area 116, a reflective mirror 104, an image-sensing device 110, and a processing circuit 112. Reflective components 106 and 108 are disposed on the sides of the sensing area 116. The reflective components 106 and 108 reflect light toward the sensing area 116. The reflective mirror 104 generates a mirror image of the sensing area 116. The reflective mirror 104 can be realized with a planar mirror. A mirror surface 118 of the reflective mirror 104 faces the sensing area 116. The image-sensing device 110 is disposed at a corner of the sensing area 116, and sensing range of the image-sensing device 110 includes the sensing area 116. The processing circuit 112 calculates the location of the pointing object 102 according to the image captured by the image-sensing device 110, so as to generate output coordinates SXY.
Please refer to FIG. 2. FIG. 2 is a diagram illustrating operating principles of the optical sensing system 100. In FIG. 2, the part above the reflective mirror 104 represents the mirror image generated by the reflective mirror 104. More particularly, the reflective mirror 104 generates a mirror image 106A of the reflective component 106, a mirror image 108A of the reflective component 108, a mirror image 110A of the image-sensing device 110, a mirror image 116A of the sensing area 116, and a mirror image 102A of the pointing object 102. It can be seen in FIG. 2 that the image-sensing device 110 senses the pointing object 102 through the optical path 204, and senses the pointing object 102A in the reflective mirror 104 through the optical path 206. Please refer to FIG. 3. FIG. 3 is a diagram illustrating an image 300 representing the image captured by the image-sensing device 110. Since the image-sensing device 110 is disposed on the left side of the reflective mirror 104, and compared with the dark line 304, the dark line 306 is closer to the left edge of the image 300, the processing circuit 112 accordingly determines that the dark line 304 is the image formed by the pointing object 102, and the dark line 306 is the image formed by the mirror image 102A. In this way, the processing circuit 112 can calculate the location of the pointing object 102 according to the dark line 304 formed by the pointing object 102 and the dark line 306 formed by the mirror image 102A. In addition, the reflective components 106 and 108 and the reflective mirror 104 reflect light to the image-sensing device 110, so that a bright zone 302 is formed in the image 300. The processing circuit 112 can more correctly obtain the location of the dark lines 304 and 306 because of the brightness contrast between the bright zone 302 and the dark lines (304 and 306). Hence, the processing circuit 112 more correctly calculates the location of the pointing object 102.
However, when the optical sensing system 100 is utilized for multi-touch operation, the processing circuit 112 can not determine which dark lines in the image captured by the image-sensing device 110 are formed by the pointing objects and which dark lines in the image captured by the image-sensing device 110 are formed by the mirror images of the point objects. For example, please refer to FIG. 4. FIG. 4 is a diagram illustrating a first situation of the optical sensing system 100 detecting two pointing objects 102 and 103. FIG. 5 is a diagram illustrating a second situation of the optical sensing system 100 detecting two pointing objects 102 and 103. FIG. 6(a) is a diagram illustrating an image 400 captured by the image-sensing device 110 in the first situation shown in FIG. 4. FIG. 6(b) is a diagram illustrating an image 500 captured by the image-sensing device 110 in the second situation shown in FIG. 5. It can be seen in FIG. 6(a) and FIG. 6(b) that the image 400 captured by the image-sensing device 110 in the first situation shown in FIG. 4 is similar to the image 500 captured by the image-sensing device 110 in the second situation shown in FIG. 5. Therefore, the processing circuit 112 can not correctly determine whether the pointing objects 102 and 103 are located as shown in FIG. 4 or as shown in FIG. 5, because the processing circuit 112 can not determine which dark lines in the images 400 and 500 are formed by the pointing objects and which dark lines in the images 400 and 500 are formed by the mirror images of the pointing objects. Therefore, according to the above description, when the optical sensing system 100 is utilized for multi-touch operation, the processing circuit 112 can not correctly calculate the locations of the pointing objects, causing a great inconvenience.